Single dose dispensers for dispensing various type of products are disclosed, for example, in U.S. Pat. No. 4,331,264 to Staar, wherein a dispenser package is formed of two foil sections joined together to provide a compressible container filled with a flowable material. The container wall includes a rupture site separating the flowable material from a chamber provided with an outlet opening. When sufficient external pressure is applied against the container wall, the flowable material bursts the rupture site and flows into the chamber to escape through the outlet opening. A blocking wall formed within the chamber downstream from the rupture site provides throttling action so that material escapes at a constant flow rate and flow strength.
The aforesaid prior art dispenser is generally effective for dispensing small amounts or unit doses of a flowable material at a constant rate of discharge, independent of pressure applied to burst the rupture site. However, since pressure is applied directly to the compressible container wall containing the flowable material, there may be a tendency for residual amounts of material to remain in the container, for example, as a film remaining between opposing walls of the container as these walls are pressed into intimate contact with each other. Thus, the aforesaid prior art arrangement may be ineffective for dispensing single doses of a medicinal preparation, wherein it is often desirable and sometimes critical to assure that the entire predetermined dosage is discharged from the dispenser.
It is accordingly an object of the present invention to provide a unit dose dispenser capable of precisely discharging an entire predetermined dosage of a composition by preventing residual quantities or films of the composition from remaining in the dispenser.
Another problem associated with the aforesaid prior art dispenser is that the use of two hands may be necessary to provide sufficient pressure to burst the rupture site for dispensing composition. This may be particularly true for elderly or infirm individuals (e.g., arthritic persons) who cannot assert the necessary pressure with one hand to dispense the composition.
Another object of the present invention is to provide a unit dose dispenser capable of easy and reliable single handed operation by requiring application of only a slight amount of pressure against a dispenser side wall for dispensing composition.
Yet a further drawback of the prior art dispenser discussed above is that the outlet opening is formed flush and in the middle of one side of the joined foil sections. The width of the opening is small in relation to the effective length of the side edge. Thus, corner portions of the side edge tend to prevent accurate positioning or contact of the outlet opening with respect to certain areas on which composition is to be directly dispensed (e.g., the cul-de-sac of the human eye in situations where the composition to be dispensed is Pilocarpine).
Yet a further object is to to provide a unit dose dispenser having an applicator tip that can be easily positioned to dispense composition directly onto a desired area.
Still a further object is to provide a dispenser wherein the applicator tip cooperates with the remainder of the dispensing structure to assure that residual quantities of composition do not remain in the tip.